And in this case, delivering an individual worker credit through the payroll tax system muddies the waters between personal income taxes and taxes paid to support Social Security.
The MPs criticise the decision to change council tax benefit at a time when the entire welfare system is being overhauled - and many individual benefits consolidated into a single Universal Credit.
Romney has recently floated the idea of an individual-deduction cap, the savings from which could easily fund a universal health insurance tax-credit system, depending on how the cap was structured.